322 THE CRUSTACEA. $ 278. 
lestium, the cerebral ganglion is entirely wanting, but, in its stead, there is 
a conspicuous thoracic ganglion under the oesophagus, from which passes off 
an equal number of nerves in front and behind, and which is succeeded, 
posteriorly, by a large nervous trunk as the abdominal cord. This cord 
has ganglionic enlargements in the three anterior abdominal segments, and 
finally divides into two branches which extend to the very extremity of the 
tail.©) With Achiheres, and Peniculus, the nervous centres consist only 
of two trunks lying on the lower surface of the abdomen, each side of the 
intestinal canal. ® 
With the Cirripedia, which are headless, the nervous centre consists of 
‘two parallel abdominal trunks, which, in their course, form six to seven 
ganglionic enlargements from which pass off, laterally, nerves to the cirri. 
The two anterior ganglia are connected by a nerve which stretches arcu- 
ately over the oesophagus, and sends filaments to the organs of mastication, 
so that a brain proper is wanting. The last two pairs of ganglia are 
blended into a single mass, which sends nerves to the cirri, and two fila- 
mens into the long tail. 
§ 273. 
The Vegetative nervous system is distinctly developed with many Crus- 
tacea. It consists of a single or of a double Splanchnie nerve. 
With the Decapoda, and Squillina, a single splanchnic nerve arises from 
the posterior border of the brain, — passes over the stomach, at the same 
time enlarging into one or two ganglia, distributes its branches to the walls 
of this organ, and, finally, enters the liver right and left. 
This nerve is reinforced by two filaments, which, conjointly with the 
nerves of the masticatory organs, are given off from the ganglionic enlarge- 
ments of the two cssophageal commissures, and, before entering the 
&planchnic nerve, send off filaments directly to the lateral walls of the 
stomach.” 
With the Oniscidae, there are two splanchnic nerves. On each side of 
the small stomach are two ganglia which connect with the brain by a short 
filament, and send off, posteriorly, small branches to the walls of the stom- 
ach.” 
With the Myriapoda, there are also two systems of splanchnic nerves. 
31 Rathké, Ibid. XIX. p. 150, Tab. XVII. fig. 
4 
» 4. 
32 Nordmann, Microgr. Beitr., Hft. 2, p. 72, 109, 
Taf. V. fig. 7, J., 6. 
33 Cuvier, Mém. loc. cit. p. 11, fig. 11, and 
Martin St. Ange, loc. cit. p. 18, Pl. II. fig. 8 
(Lepas) ; also Wyman in Si "iman’s Amer. Jour. 
XXXIX. 1840, p. 182 (Otion).* 
1 We are indebted to Brandt for very complete 
contributions on the sympathetic system of the 
Decapoda ; see his Bemerk. tiber d. Mundmagen- 
oder Kingeweidenerven der Evertebr. loc. cit. p. 7, 
Tab. I. fig. 1-3 (Astacus and Squiila), (also in the 
Ann. d. Sc. Nat. V. 1836, p. 87, Pl. IV. and in the 
Mediz. Zool. If. Taf. XI. fig. 1, i.); see, also, 
* [§ 272, note 33.] Subsequent researches have 
shown that with some at least of the Cirripedia, 
there is 4 proper brain furnishing nerves to the 
organs of sense ; see Darwin, Monogr. of the sub- 
Krohn, Isis, 1834, p. 529, Taf. XII. fig. 1-4, and 
Schlemm, De hepate ac bile Crustaceorum et Mol- 
luscorum, loc. cit. p. 16, Tab. I. fig. 2, Tab. IT. fig. 13 
(Astacus fluviatilis). Suckow (loc. cit. p. 62, Tab. 
XI. fig. 7, g.) in the Crawfish, and Newport (Philos. 
Trans. 1834, Pl. XVII. fig. 40, f.) in the lobster, have 
observed only a single splanchnic nerve, which they 
have regarded as a cardiac nerve. Audouin and 
Miine Edwards, on the other hand, have described 
and figured with both the Macrura and the Bra- 
chyura, double splanchnic nerves, but the single 
one was entirely overlooked, 
2 Brandt, Bemerk. &c. p. 14, and Medizin. Zool, 
II. p. 75, Taf. XV. fig. 27, ¢. 
class Cirripedia, &c., p. 48 (Lepas). Even in the 
description referred to above, of Otion, by Wyman 
in Silliman’s Jour., a brain is really spoken of. — 
Ep. 
